The effect of Chinese wild blueberry fractions on the growth and membrane integrity of various foodborne pathogens

The objective of this study was to evaluate the antibacterial effect of Chinese wild blueberry extract and its fractions against Listeria monocytogenes, Staphylococcus aureus, Salmonella Enteritidis, and Vibrio parahaemolyticus. Chinese wild blueberry (Vaccinium uliginosum) crude extract (BBE) was obtained using methanol extraction, and sugars plus organic acids (F1), phenolics fraction (F2), and anthocyanins plus proanthocyanidins (F3) fractions were separated using C-18 Sep-Pak columns. The minimal inhibitory concentration and minimal bactericidal concentration of each fractional component were determined using a two-fold-serial dilution method. Nucleic acid leakage (OD260 nm ) and protein release (Bradford protein assay) were determined by spectrophotometry, to evaluate the permeability of the cell membrane. F3 was found to exhibit the greatest antimicrobial activity against the four tested strains, followed by F2, F1, and BBE. V. parahaemolyticus was the most sensitive to the all fractions, followed by S. Enteritidis, L. monocytogenes, and S. aureus. Survival curve analysis showed that the number of bacteria decreased from six log colony-forming units (CFU) to less than 10 CFU after bacteria were treated with fractions for 12 hr, which demonstrated the bactericidal effect of blueberry fractions. Furthermore, when the pathogens were treated with fractions for 2 hr, the OD260 nm and OD595 nm values increased significantly (P < 0.01), which indicated the significant release of nucleic acid and protein. The results from this study indicated that blueberry fractions, especially F3, inhibited the growth of foodborne pathogens by damaging their cell membrane, and may be developed as a natural preservative to prevent and control foodborne pathogens. PRACTICAL APPLICATION: A blueberry crude extract and its sugars plus organic acids, phenolics, and anthocyanins plus proanthocyanidins fractions, inhibited the growth of foodborne pathogens by destroying their cell membrane. Therefore, Chinese wild blueberries have potential as a natural preservative to prevent and control foodborne pathogens.